Fix a bug where inbox passed rooms into does_user_exist

This needs to verify the type of the request at the moment where we need
to decide if the inbox owner exists. We can't return false because that
would drop the required markers from resetting the count. We can't
return `can_access_room` because then the message telling the user that
he has been removed from a room would arrive to the user at a time when
he's not a member of the room anymore. So we simply must return true
from here.

src/inbox/mod_inbox.erl

@@ -229,19 +229,19 @@ disco_local_features(Acc) ->
                             Msg :: exml:element(),
                             Dir :: mod_mam_utils:direction()) -> mongoose_acc:t().
 maybe_process_message(Acc, From, To, Msg, Dir) ->
-    case should_be_stored_in_inbox(Acc, From, To, Msg, Dir) of
+    Type = get_message_type(Acc),
+    case should_be_stored_in_inbox(Acc, From, To, Msg, Dir, Type) of
         true ->
-            do_maybe_process_message(Acc, From, To, Msg, Dir);
+            do_maybe_process_message(Acc, From, To, Msg, Dir, Type);
         false ->
             Acc
     end.
 
-do_maybe_process_message(Acc, From, To, Msg, Dir) ->
+do_maybe_process_message(Acc, From, To, Msg, Dir, Type) ->
     %% In case of PgSQL we can update inbox and obtain unread_count in one query,
     %% so we put it in accumulator here.
     %% In case of MySQL/MsSQL it costs an extra query, so we fetch it only if necessary
     %% (when push notification is created)
-    Type = get_message_type(Acc),
     HostType = mongoose_acc:host_type(Acc),
     case maybe_process_acceptable_message(HostType, From, To, Msg, Acc, Dir, Type) of
         ok -> Acc;
@@ -573,18 +573,21 @@ get_message_type(Acc) ->
 %%%%%%%%%%%%%%%%%%%
 %% Message Predicates
 -spec should_be_stored_in_inbox(
-        mongoose_acc:t(), jid:jid(), jid:jid(), exml:element(), mod_mam_utils:direction()) ->
+        mongoose_acc:t(), jid:jid(), jid:jid(), exml:element(), mod_mam_utils:direction(), message_type()) ->
     boolean().
-should_be_stored_in_inbox(Acc, From, To, Msg, Dir) ->
+should_be_stored_in_inbox(Acc, From, To, Msg, Dir, Type) ->
     mod_mam_utils:is_archivable_message(?MODULE, Dir, Msg, true)
     andalso mod_inbox_entries:should_be_stored_in_inbox(Msg)
-    andalso inbox_owner_exists(Acc, From, To, Dir).
+    andalso inbox_owner_exists(Acc, From, To, Dir, Type).
 
--spec inbox_owner_exists(mongoose_acc:t(), jid:jid(), jid:jid(), mod_mam_utils:direction()) ->
+-spec inbox_owner_exists(
+        mongoose_acc:t(), jid:jid(), jid:jid(), mod_mam_utils:direction(), message_type()) ->
     boolean().
-inbox_owner_exists(Acc, From, _To, outgoing) ->
+inbox_owner_exists(_, _, _, incoming, groupchat) ->
+    true;
+inbox_owner_exists(Acc, _From, To, incoming, _) -> % filter_local_packet
     HostType = mongoose_acc:host_type(Acc),
-    ejabberd_auth:does_user_exist(HostType, From, stored);
-inbox_owner_exists(Acc, _From, To, incoming) ->
+    ejabberd_auth:does_user_exist(HostType, To, stored);
+inbox_owner_exists(Acc, From, _To, outgoing, _) -> % user_send_packet
     HostType = mongoose_acc:host_type(Acc),
-    ejabberd_auth:does_user_exist(HostType, To, stored).
+    ejabberd_auth:does_user_exist(HostType, From, stored).